The present invention relates to the field of automatic data handling and, more particularly, to apparatus and methods for reading information that is recorded on a record carrier. Specifically, the present invention provides apparatus and methods for detecting positionally encoded information on a record carrier, which positionally encoded information preferably includes at least one humanly intelligible character so that the record carrier is both machine-readable and humanly readable.
Various techniques exist for recording information on a record carrier. In order that information on a record carrier may be automatically processed, different types of machine-readable codes have been developed. One of the most common types of machine-readable codes is a "position code." Generally, information is recorded on a record carrier in position code format by dividing the record carrier into one or more zones, subdividing each zone into a plurality of discrete areas, and, then, by marking, punching, notching, embossing, magnetizing, or the like, particular ones of the discrete areas to encode the information. One type of position code is the familiar "two-out-of-five" position code.
Positionally encoded record carriers are utilized extensively. Illustrative of such is the familiar machine-readable test answer sheet. A desired answer is designated by marking with a dark pencil a discrete area on the test answer sheet. A machine is then employed to optically read the positionally encoded answers. It is important that the answers are accurately read. Only then is the correct test score obtained.
Unfortunately, errors are easily introduced. For example, during a test an answer may be changed by erasure of a mark in one discrete area and placement of another mark in a different discrete area. If the erasure is incomplete, a "spurious mark" can remain and cause a reading error. Moreover, unintentional marks due to dirt, smudges, etc. can also occur to constitute further sources of spurious marks. In order to insure that reading errors do not result, it is necessary to provide a reader which exhibits high resolution optical position code sensing characteristics to discriminate against spurious marks.
Generally, positionally encoded record carriers include a separate zone where the machine-readable position code, which is not readily humanly intelligible, appears in a humanly intelligible form, for example, printed alphanumeric characters, so that the information that is recorded on the record carrier in machine-readable position code is also humanly readable. On the test answer sheet, for example, each zone is labeled with a question number and each discrete area is provided with a fixed label to identify, in a humanly intelligible form, the various multiple-choice answers, e.g., "a," "b," "c," "d" or "e."
In some cases, however, variable information must be positionally encoded on a record carrier, and, therefore, fixed labels cannot be employed. In an employee attendance recorder system, for example, an employee is given a time card which he inserts in a time clock/imprinter to maintain a record of the hours which he has worked. The time card is utilized to compute the employee's pay. The time data may be positionally encoded on the time card and, therefore, machine-readable so that the employee's pay can be computed automatically by data processing equipment. Desirably, the time data is also humanly readable so that the employee can visually check the accuracy of the "in" and "out" times which are recorded on his time card. Since fixed labels cannot be employed due to the variable nature of the time data, a need exists for a technique by which variable machine-readable positionally encoded information on a record carrier, such as "in" and "out" times in an employee attendance recorder system, may be made humanly readable, for example, to enable the employee to verify the accuracy of the times recorded on his time card to assure him that his pay will be accurately computed.